1. Field of the Invention
The present invention relates to a mobile terminal, and more particularly, to a dual mode mobile terminal and controlling method thereof. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for receiving an LTE signal without a data rate fall in the course of measuring a quality of a CDMA signal.
2. Discussion of the Related Art
Generally, a dual mode mobile terminal is a mobile terminal capable of supporting two species of wireless communications differing from each other in communication system. The dual mode mobile terminal is mainly used in an area whether heterogeneous communication networks coexist. As a representative example of the dual mode mobile terminal, a mobile terminal available for both LTE (long term evolution) wireless communication and CDMA (code division multiple access) wireless communication is ongoing to receive wide attention. Although a dual mode mobile terminal capable of communicating with both LTE network and CDMA network are taken as an example for the present invention, it is apparent to those skilled in the art that the present invention is applicable to other species of wireless communication systems.
In the LTE wireless communication, an MIMO scheme for transmitting and receiving signals using a plurality of transmitting antennas and a plurality of receiving antennas is adopted. Once the MIMO scheme is adopted, a transmitting or receiving stage is able to increase capacity and enhance performance using a plurality of antennas. Moreover, the CDMA wireless communication has needed multiple antennas for diversity scheme since EV-DO REV. A. In this disclosure, MIMO can be called ‘multiple antennas’.
In order to receive one whole message, MIMO system does not depend on a single antenna path. Instead, in the MIMO system, data is completed by collecting to combine data fragments received via plural antennas together. If the MIMO system is used, it is able to data rate can be improved within a cell area having a specified size. And, it is also able to increase system coverage while securing a specific data rate. Moreover, the MIMO system is widely applicable to a mobile communication terminal, a relay and the like. According to the MIMO system, it is able to overcome the limited transmission traffic in mobile communication of the related art having used a single antenna.
Meanwhile, in a dual mode terminal of the related art, it may cause a problem that transmission/reception of LTE signals is interrupted in a specific situation due to the limitation put on the number of antennas loadable in one terminal device.
FIG. 1 is a diagram for a structure of a single radio frequency receiver chain-dual mode terminal according to a related art.
Referring to FIG. 1, a single radio-dual mode terminal includes an LTE modem and a CDMA modem. And, a diplexer performs multiplexing of DCN (data core network) frequency band and PCS (personal communication service) frequency band and demultiplexing thereof. Moreover, an antenna 0 and an antenna 1 are simultaneously switched between the LTE modem and the CDMA modem.
FIG. 2 is a diagram for explaining a problem that may be caused by a general single radio frequency receiver chain-dual mode terminal.
Referring to FIG. 2, in case that a terminal, that is communicating with an LTE network, attempts a handover into a CDMA network, it stops a reception of an LTE signal from an LTE base station (eNodeB) during about 6 ms, as shown in FIG. 2, and then measures a quality of a CDMA signal. The measured quality of the CDMA signal is transmitted to the LTE base station via an LTE modem.
In this case, the quality of the CDMA signal means eHRPD (enhanced high-rate packet data) measurement. Moreover, eHRPD is a new version of 1xEV-DO upper layer protocol stack developed by 3GPP2 Standard committee to prepare for the wireless communication network interoperability with LTE.
An intermediate time of the LTE signal for this quality measurement is called a measurement gap. During this measurement gap, the antenna 0 and the antenna 1 of the dual mode terminal of the related art are connected to the CDMA modem by switching. In particular, this measurement gap means interruption of reception/transmission of LTE signal, which consequently means that frequency efficiency is lowered.
The present invention intends to propose an apparatus for performing CDMA signal quality measurement without generating a measurement gap and method thereof.